What is the nature of love between the poet and his beloved in the poem, "The Definition of Love"?

In "The Definition of Love," Andrew Marvell describes an ill-fated love, as it seems that the speaker and his beloved cannot be together.
The poem suggests that the speaker blames "Fate" for the separation between him and his beloved. At the start of the poem, the speaker laments that his love has been "begotten by Despair / Upon Impossibility" (lines 3-4), that it is born of "Magnanimous Despair" (5). This despair has made him see something that "Hope" could not have shown him, which indicates that the tragic circumstances keeping he and the beloved apart have made his love stronger. 
In the third stanza, the speaker moves into his main argument, which is that Fate is to blame for keeping he and his beloved apart. He says that he could have overcome "Despair," but "Fate does iron wedges drive, / And always crowds itself betwixt" (11-12). Something has come between the speaker and his beloved that he feels is out of their control. He next describes Fate as "jealous" when looking upon the feelings he and his beloved have for one another, saying that if their love were to succeed, Fate would be defeated and no longer have power (14-16). 
The next stanza continues the speaker's comments on Fate, as he goes on to say that Fate has used "her decrees of steel" to keep the lovers at "distant poles" (17-18). Fate has kept them apart, and the choice of the word "steel" suggests the power and inflexible nature of Fate. The speaker later describes he and his beloved as "parallel" lines that, "Though infinite, can never meet" (27-28). The concluding stanza summarizes the speaker's main idea: 

Therefore the love which us doth bind
But Fate so enviously debars,
Is the conjunction of the mind
And the opposition of the stars. (29-32)

The nature of the love between the speaker and the beloved is clear here: they are bound by their love and their own free will to love each other, but Fate and "the stars" oppose their union, so the lovers cannot be together.